When maintained on oral naltrexone for narcotic blockade, postaddicts sometimes resort to the use of non-narcotic abuse drugs. Therefore, it is desirable to determine if the simultaneous use of various non-narcotic abuse drugs might interfere with the narcotic blockading efficacy of oral naltrexone, as determined in laboratory animals. The proposed work for the continuation of this project would be principally the extension of the program to include additional non-narcotic abuse drugs, e.g., fenfluramine HCl (Pondimin) and other scheduled anorexigenic drugs, in studies of their possible effect on the narcotic blockading action of oral naltrexone, as determined by the prevention of the Straub tail reaction produced by morphine in mice and prevention of the loss of righting reflex produced by morphine in rats. Also, it has been demonstrated in the previous work that cocaine, amphetamine, and some other amphetamine-like drugs potentiate morphine in the production of the Straub tail reaction in mice and increase the dosage of oral naltrexone required to block this narcotic effect. Investigations will be carried out in effort to determine if this potentiation is due to a noradrenergic, dopaminergic, etc., action of these added CNS stimulants.